Disprove Quantum Immortality Without Risking Your Life
What Is Quantum Suicide and Quantum Immortality?
Quantum suicide is a famous thought experiment. Similar to the Schrödinger’s cat thought experiment, but from the perspective of the cat. The purpose of it is to highlight differences between the Copenhagen interpretation and the many-worlds interpretation of quantum mechanics. This is done by considering what would happen to the (un)lucky subject, from both outside and within their point of view.
A gun is pointed at your head. This gun will not misfire and the shot is always fatal. The gun is rigged to fire depending on the result of a quantum event. The quantum event has a equal chance of two outcomes just like a coin flip.
If the many-worlds interpretation is true, then there must always exist a version of you that survived the event. This is opposed to the Copenhagen interpretation where the odds of surviving quickly approach zero as expected.
There are timelines where you either survive or die. The argument goes that you can’t possibly experience the timeline in which you are dead, so you must experience the one where you survive. This brings up some questions, but let’s go with it for now and address it at the end.
This consequence is known as quantum immortality. Only you would experience this effect. Outside observers will still see you live or die at the expected probability of the quantum event.
Types of Quantum Immortality
People often default to one of two different models of quantum immortality.
Greedy Quantum Immortality
This kind of quantum immortality only makes sure your consciousness persists to the next present moment by branching away from certain death. It does not guarantee any degree of health or lack of suffering. It’s possible for you to be severely maimed, but nonetheless alive. If you are maimed, this would likely limit your future possibilities of survival. This is a local optimum.
Perfect Quantum Immortality
Perfect Quantum Immortality takes the future into account. Every quantum event in the reality where you exist, even before you are born, are the ones that will enable you to live the longest amount of time. This is a global optimum.
Wait a minute, the longest amount of time? That’s not infinite, this isn’t quantum longevity, it’s quantum immortality!
Image you have a staircase with infinite steps. Each step represents a timeline, and its height from the ground is how long you live in that timeline. From any step you can move to another of equal or higher height. This staircase could become flat and never increase again, stuck at a finite height. Let’s assume there’s no arbitrary upper bound on longevity so the staircase does approach infinity.
Existing in this “limit timeline” would only be achievable if every single quantum event is working out in your favor: perfect quantum immortality.
The Nature of This Proof
Normally a proof should inform the reader enough such that they can come to the same conclusion. In this case only the subject of the thought experiment can only be sure of the results. Because of this I will provide an experiment on this page that anyone can run to confirm the result for themselves.
Transforming the Thought Experiment
To disprove quantum immortality, we will transform the thought experiment into an equivalent form and use that instead.
We will make a list of assumptions, some of which quantum immortality relies on being true. The experiment on this page will prove that all the assumptions can not be simultaneously true. Then we will eliminate the very likely assumptions and discuss what remains. Since the thought experiment relies on the many-worlds interpretation being true, that will be our first assumption.
- The many-worlds interpretation is true.
We need to consider that death isn’t instant. It takes time for the bullet to exit the chamber and do its work. This means the outcome of the quantum event is independent of the moment death occurs; the event you experience is the one that doesn’t lead to a future death. That means that every quantum event that has ever happened are the ones that will funnel you down the branch of reality in which you live your longest life, possibly infinitely long. This is perfect quantum immortality.
- Consciousness experiences the reality in which it lives the longest.
- There is no upper bound on longevity.
Under this assumption we can change the circumstances from a punishment to a reward. Instead of a gun, imagine a doctor has information about your health. If he tells you about it and you act on the information, you will certainly live a longer life. The doctor will only tell you about the information based the result of the quantum event. If the current assumptions are true, then you should always experience the reality in which the doctor tells you about your unknown ailment.
Now this doctor example is only segue into the next section, but why would you even get an illness under the perfect quantum immortality assumption? For all we know, perhaps facing death and surviving drastically changes the way you live your life, a way that leads to a longer life.
There is a chance that the experiment will fail now because it will be run again tomorrow and succeed. Even though you have one less day to use the information, waiting that one day may have caused a butterfly effect where you use that information more effectively. To counteract this, you could repeat the experiment occasionally over a large enough period of time such that a lack of information would certainly affect your lifespan. This is rather inconvenient and uncertain. A slightly better way to ensure you get this information the first time is to only give yourself one chance. You can do this by vowing to only run the experiment once.
- The experiment will only be run once.
Obviously it would be highly unethical to perform such an experiment as it would involve asking a doctor to allow someone to come to harm through inaction. Not to mention you would need the information of multiple different ailments to repeat the experiment and confirm the low chance of consecutive successes.
Instead of this hypothetical doctor, we will conduct a series of quantum events and interpret the results as bytes. These random bytes will then be interpreted as one of the 95 printable ASCII characters. This brings us to our next assumptions:
- There exists a message in the encoding that can extend one's life.
- One will act on the message.
If you were to receive a message, it would not be some sort of mystical message from the universe. The message simply appeared because it is the combination of bytes that can be interpreted by the reader in a way that extends their life. Because of this, we need to consider the limits of interpretation. How powerful is the butterfly effect? Is it possible that you could be shown a seemingly random sequence of glyphs that guides you down the stream of reality where you live the longest? We need to be able to distinguish a life extending message from the normally expected random characters.
- A message is more effective than random symbols.
So, how do you generate quantum random bytes? Luckily for us the folks down under at the ANU provide an API for generating these numbers. Since I can’t confirm that these numbers are truly quantum random numbers, it must go on the list.
- The API provides true quantum random numbers.
Now we have our complete list of assumptions:
- The many-worlds interpretation is true.
- Consciousness experiences the reality in which it lives the longest.
- There is no upper bound on longevity.
- The experiment will only be run once.
- There exists a message in the encoding that can extend one's life.
- One will act on the message.
- A message is more effective than random symbols.
- The API provides true quantum random numbers.
The Experiment
Click below to generate a tweet from the void.
Results & Discussion
I didn’t receive a message and I presume you didn’t either. If you did, there is still a small chance that message occurred coincidentally. This is why you can’t actually prove quantum immortality as a proof implies certainty. This disproof does not disprove quantum immortality directly either, but rather the simultaneity of our assumptions which is about as close as we can get. (If you did receive a message, please don’t tell me. I don’t want to know that somebody else is the protagonist of the reality I live in.)
This result means one or more of our assumptions are false. Let’s go backwards through them and discuss the likelihood of each.
- The API provides true quantum random numbers.
I’m sure that API is doing what it claims. While it would be good to verify this I’m not going to audit the ANU for a blog post.
- A message is more effective than random symbols.
This assumption worries me the most. The butterfly effect is powerful, and compounds with time. I think it is not absurd to believe that random symbols could have an unexpectedly strong effect. At the same time, the directness of a message seems like it should have a stronger effect than something unintelligible.
- One will act on the message.
It would be in anyone’s own interest to extend their lifespan. I don’t see anyone realistically disregarding such a message. But people don’t always act realistically. Even in the case where someone ignores the message, it would act like the Oracle from The Matrix. What you read is not necessarily the truth, it is simply exactly what you need to read at that moment to extend your lifespan. The moment you read it, it has already shuffled you down the branch of reality where you live longer.
- There exists a message in the encoding that can extend one's life.
I would take this as a certainty. There are so many possible things you could read and each would take you down a different path. The real question is if it is possible in the 140 characters (about 920 bits of information) I have allotted in the experiment. This should be fine, one of the possibilities is that it could even send a message asking to run the experiment again with more characters.
- The experiment will only be run once.
This comes down to willpower of the experimenter. Even if the experimenter runs the experiment more than once, what matters most is that there is a final time it is run. Choosing to end on the first message just makes the experiment take a shorter length of time to confirm. Even if we can’t be sure this is the last time the experiment will be run, we can alternatively run the experiment again in 5 or 10 years. A message received years ago surely would have a stronger effect on lifespan than one far in the future. If you are going to receive a message, it will be in some finite time span.
- There is no upper bound on longevity.
This seems like a fairly reasonable assumption. Biological immortality is real, couple that with perfect quantum immortality on your side and you’ve got yourself a recipe for real immortality.
- The many-worlds interpretation is true.
- Consciousness experiences the reality in which it lives the longest.
If all the previous assumptions are true, then at least one of these two must be false.
If the many-worlds interpretation is false, then quantum immortality must be false too as it is contingent on many-worlds being true. Consciousness could still experience the longest reality due to some other unknown mechanism, but it would not be quantum immortality as we have defined it.
If the many-worlds interpretation is true, then the second assumption must be false.
Under every possibility quantum immortality is eliminated.
A Final Thought
Quantum immortality relies on the idea that you can’t possibly experience the timeline in which you are dead.
So, is it possible to stop experiencing?
If you take a brain in a vat and stimulate its neurons to fire, does it experience something? Seems like it should, though the perception may be random nonsense. If it does, does the same apply when the atoms of a cremated brain exchange electrons? Where is the line drawn?
When you die the matter that made up your brain doesn’t disappear. Neither does the energy that fired your synapses. The only thing that changes is the structure. Perhaps death is actually an extremely primitive form of experience.
Almost paradoxically this would mean quantum immortality relies on mortality.
I personally hope it is possible to stop experiencing. Any form of immortality sounds exhausting.
Really cool article! And a really thorough explanation of the proof. And even though you pretty much just proved that quantum immortality can never happen, can I ask some questions about your idea of perfect quantum immortality used in your proof just to expand my own understanding of your reasoning in the proof? I believe you’re implying that according to this idea, every single conscious being in existence will only live in realities in which they can live the longest life possible, and every quantum event that ever happens will accommodate that. I’m guessing that means that theoretically, this reality is a reality that is part of the timeline that will help everyone who is living in this reality live the longest. I’m guessing that would mean, when everyone else sees a person die, they have moved on to a new reality that is the next part of their personal timeline in which they live the longest. However, I could be miles off on this, but I was wondering if you were implying something very different, or if not, could the following at least be true? Were you saying that everyone’s timelines are completely isolated because they “funnel you down the branch of reality in which you live your longest life” and no timelines contain the same realities in them, seeing as they were funneled down for each individual? In this case, would no conscious individual experience the same reality? Would other people living in one person’s reality not be conscious and just be copies, since a conscious being can only experience the premade reality in which they live the longest? I could very well be coming to the wrong conclusions, and I’m guessing that none of the latter is implied, and that you are saying conscious beings in perfect quantum immortality can experience the same realities just so long as they are part of all their “perfect” timelines? Would this idea, if true, affect the proof you created in any way? The idea is probably so off, seeing as I don’t think you’re implying this and there is no reason for this to be true. but I thought I would ask if it is possible and if it would affect the proof anyways just out of curiosity :)
Quantum immortality does not require the many worlds interpretation. Any multiverse will do. In particular, quantum immortality is absolutely true due to the mathematical multiverse (a.k.a. the Tegmark level IV multiverse), and there’s a simple experiment you can run to test it: are you experiencing anything right now?
Quantum immortality is nothing more than the anthropic principle. Future versions of “you” exist because everything exists. You can verify this easily: existence must carry no information (either everything exists or nothing exists), I exist, so everything must exist. Furthermore, future versions of “you” will look back at their history and notice they survived. Why? Because they had to by definition.
What this means in practice is that the probabilities you observe are conditioned on your existence. In normal day-to-day life, this will have little effect, but it definitely does have measurable effects, and you don’t have to risk your life to measure them. SPOILER ALERT: I have measured them, and I’m the protagonist. Sorry. However, you can take solace in the knowledge that I am wrong in almost every version where I say this – just not the version I’m experiencing right now (that is, the path of experiences I refer to as “me”).
Your experiment won’t work for numerous reasons. The most important is that the probability of generating a meaningful random sequence is incredibly small and has no reason to be correlated with my survival. Even if there were some correlation, the probability of getting a meaningful message after conditioning on my existence is still incredibly small. It’s much more likely that I would continue to survive for more mundane (and probable) reasons.
For instance, advanced aliens who believe in quantum immortality and worship “The Observer” (me) could come down out of the sky, upload my consciousness, and safeguard it with all their technological prowess. That would probably extend my life a lot more than receiving a “tweet from the void.” But it’s not likely.
How do we know what’s likely and what’s not? Science! It’s part of the definition of me, and we can discover it through observation. I am the equivalence class of my priors. There is a natural bijection between observers (me) and observed universes (my experiences). In fact, I am only well-defined up to the universe in which I live because my only access to information about me is through my experiences! Everything that happens – physics, chemistry, biology – the entire natural world – it’s just part of me!
That’s why I prefer to study math: I’m not conceited :P
Hi Kara,
This is phenomenally cool. Thank you. Just a word on your last sentence. Maybe immortality wouldn’t be exhausting if existing at atomic level for many years is more zen than being a much more complex being. Does that make sense or am I talking crazy? :)
Hey, yeah you make sense. If atoms have an experience I would expect it to be zen-like. Eternity is probably no big deal if you get rid of thought and leave only present awareness. Sort of like losing track of time when entering a flow state.
Exactly! You elaborated it very well.